1. Technical Field
The present invention relates to dispensing apparatus and in particular to a portable self-contained pneumatic gun for dispensing metered and/or mixed single or plural-component flowable materials. More particularly, the invention relates to a portable dispensing pneumatic gun which is self-contained and internally muffled for delivering flowable materials from single or two-component packages wherein the flowable materials are metered and/or mixed closely adjacent to the point of dispensing or application.
2. Background Information
An ever increasing number of products used in everyday life require the dispensing of liquid or semi-liquid flowable materials in one form or another for their manufacture. These flowable materials typically comprise two-component reactive resins: however, single component flowable materials are also frequently employed in such manufacture. The types of materials dispensed include virtually any flowable liquid, semi-liquid, or paste such as epoxies, polyurethanes, silicones, polyesters, acrylics, polysulfides and phenolics, for example. Common commercial manufacturing processes in which such materials are used include injecting precise amounts of mixed resins into molds, encapsulating electric components with insulating resins, applying continuous beads of structural adhesives, injecting polyesters into closed molds, sealing joints with two-part polysulfides, and numerous other functions requiring accurate material control and delivery. Examples of product applications for these materials and processes include under-the-hood electronic assemblies and safety devices for the automotive and trucking industry; encapsulation of magnetic and other advanced electrical devices for the aerospace industry; component mounting, security potting and gun-type applications for circuit board assemblies and components and apparatus such as switches, power supplies, heating assemblies, and other electronic components for the appliance industry.
Thus, as the aforesaid flowable materials continue to be consumed in increasing quantities the demand for precise liquid and semi-liquid dispensing apparatus is also growing at an accelerated rate. The industry is continually searching for more reliable, efficient and accurate metering and/or mixing and dispensing apparatus for flowable materials for a variety of purposes. For example, a particular application may require that an apparatus efficiently and accurately dispense such materials ranging in amounts from less than 1 cubic centimeter to many gallons. However, although, the industry is calling for more exacting apparatus, it is also requiring that the apparatus design be simple, straightforward and capable of being operated by production personnel or conveniently integrated with automation devices such as robots and conveyor systems. Problems currently exist because many prior art metering, mixing and dispensing apparatus are immobile, requiring that the work be brought to the apparatus which most often is inefficient and impractical.
Moreover, the design of many types of the prior art metering, mixing and dispensing apparatus, due to their bulky nature and the inability to position the apparatus in close proximity to the work, include lengthy hoses for transport of the metered and/or mixed material, the components of which often begin to react prematurely, sometime before it is actually dispensed which is highly undesirable. Rather, it is preferable that the flowable materials be metered and/or mixed as closely as possible to the point of dispensation or application to avoid premature reaction of the materials. Also, locating the metering and mixing components of the apparatus as closely as possible to the dispensing point increases metering accuracy and control.
A most common problem with known dispensing guns is the matter of overrun discharge or dribbling of the flowable materials when dispensation is stopped or terminated. The slow release of pressure on the piston member causes the materials to continue to flow at a decreased rate until pressure is fully relieved resulting in inaccurate dispensing and improper ratios of mixed materials. Where two-component materials are dispensed simultaneously, they may have different flow and viscosity characteristics accentuating the inaccuracy of desired delivery. Loss of precise delivery of desired amounts is a frequent problem especially where small volumes are dispensed.
The structure of the subject apparatus is different from the prior art equipment. The subject improved dispensing gun of the pneumatic type of this invention is portable and self-contained. The need exists for an improved metering, mixing and/or dispensing apparatus in which single or plural-component flowable materials are metered and/or mixed adjacent to the point of dispensing and/or application, and which is portable enough to be handled by a human operator and/or which may be readily integrated with robotic or automation systems.